Yellowstone supervolcano fed by bigger plume

The underground volcanic plume at Yellowstone in the US may be bigger than previously thought, according to a new study by geologists.

The volcanic hotspot below Yellowstone feeds the hot springs, mud pots and geysers that bring millions of visitors to the US national park each year.

But the Yellowstone "supervolcano" has erupted violently in the distant past and could do so again at some point.

The new study is set to be published in Geophysical Research Letters journal.

In 2009, researchers used seismic waves from earthquakes to build up an image of the hotspot beneath Yellowstone, which straddles the US states of Wyoming, Montana and Idaho.

The authors of the latest work used variations in the electrical conductivity of rocks to produce a new picture of the plume.

This conductivity is a property of the molten silicate rocks and the hot briny water that is naturally present in them.

"It's like comparing ultrasound and MRI in the human body; they are different imaging technologies," says co-author Michael Zhdanov, a professor of geophysics at the University of Utah in Salt Lake City.